The present invention relates to a cleaning device for cleaning the peripheral surface of a photoconductive drum in an electrophotographic copier. More particularly, the invention is directed to a cleaning device which is capable of being brought into, and out of, contact with the peripheral surface, and which comprises a spray-tube for the supply of cleaning liquid, cleaning elements, such as a scraper, a cleaning roller, and a lever arrangement which positions the cleaning roller and the scraper.
In copiers utilizing liquid toner, the cleaning of the photoconductor is, in most cases, effected by means of a rubber-elastic scraper, in conjunction with a roller, the latter being made of a foamed material. A device of this type is described in German Auslegeschrift No. 2,600,950. In this known cleaning device spring arrangements are provided which attempt to pivotally lift the cleaning device from the photoconductor-drum. In order to prevent such separation, a lever, fastened to an outer end of a supporting shaft of the cleaning device, is provided which opposes the spring force of the spring arrangements and against the elastic forces of the cleaning device. By rotary movement, the free end of the lever is brought into engagement with a securing member, as a result of which the cleaning device is brought into pressure-contact with the peripheral surface of the drum. First and second lever arrangements which are in engagement with one another are provided for carrying the cleaning elements of the cleaning device.
A cleaning arrangement for a photoelectrostatic copier, with a scraper, is described in German Offenlegungsschrift No. 2,758,766. According to this disclosure, the copier comprises a first arrangement which brings the scraper out of contact with the photoconductor-drum, when the copier is not operating, and a second arrangement which pivots a cleaning roller out of contact with the photoconductor-drum or, at least, reduces the contact pressure thereof. In this arrangement, liquid developer is supplied as cleaning liquid to that portion of the photoconductor-drum which is located between the scraper and the squeeze-off roller. The apparatus for actuating the scraper and the squeeze-off roller are coupled together in such a manner that the scraper and the squeeze-off roller are simultaneously brought into, and out of, contact with the photoconductor-drum.
Cleaning devices are likewise described in U.S. Pat. Nos. 4,080,059 and 4,165,172, in which the device includes a cleaning roller and a rubber-elastic scraper, as well as a spray-tube for the supply of the cleaning liquid. The tube is located in such a manner that the cleaning liquid is dammed-up between the scraper, which is bearing against the peripheral surface of the photoconductor-drum, and the squeeze-off roller.
The known cleaning devices share the feature that, during the copying process, the rubber-elastic scraper, and the cleaning roller, together, are pivoted into contact with the photoconductor-surface. The cleaning liquid for wetting and rinsing the photoconductor surface is supplied between the scraper and the cleaning roller which, for example, may be of a foamed material. In this step, the cleaning roller is utilized primarily for dissolving-off the residual toner-image from the photoconductor-surface. At the same time, the rubber-elastic scraper scrapes the liquid toner from the photoconductor-surface in such a manner that this surface is afterwards clean and dry. As a result of supplying cleaning liquid, generally liquid toner, between the cleaning roller and the scraper, the zone between the roller and the scraper is wetted, thus diluting the thickened toner adhering to the photocondcutor-surface in front of the scraper, and allowing for the toner to be rinsed away. In the case of drum-lengths of up to a maximum of 350 mm, which are used for copying-formats DIN A4 and DIN A3, the diluted toner can still flow away sufficiently rapidly towards the edges of the drum, without being dammed-up between the cleaning roller and the scraper. If, however, longer drums are to be cleaned, the problem arises in that toner is dammed-up between the scraper and the cleaning roller to an excessive height, because it cannot flow away to the edges quickly enough due to the long drum-length. If now, following completion of the copying and cleaning operation, the cleaning device is lifted off, the dammed-up toner runs off downwardly, over the drum surface, in a flood, resulting in possible wetting of the sub-assemblies, such as the corona and the paper feed devices, which are located in the vicinity of the photoconductor-drum, thus adversely affecting their operation.
Another disadvantage of a cleaning device of this type is that residues of toner liquid can dry on the surface of the drum. Because it is necessary that these residues be dissolved before the start of a new copying operation, a preliminary process step of applying the developer liquid or the cleaning liquid, which is generally the solvent for the toner, is required, as a result of which dissolving-off process the preliminary running time of the copier before a new copying cycle, is lengthened.